Self-Aligning Mechanisms in Passive and Powered Exoskeletons

ABSTRACT

An exoskeleton device that includes an artificial joint and a frame member extending from the artificial joint. The frame member is configured for extension over a limb of a user. The exoskeleton device also includes a self-aligning mechanism connected to the frame member. The self-aligning mechanism includes three passive degrees of freedom (pDOF) provided in a prismatic-revolute-revolute (PRR) configuration. The self-aligning mechanism also includes a limb attachment member configured for mechanically coupling to a portion of the limb of the user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/992,631, filed Mar. 20, 2020 and titled“SELF-ALIGNING MECHANISMS IN PASSIVE AND POWERED ORTHOSES”, the entiretyof which is incorporated herein by this reference.

GOVERNMENT RIGHTS

This invention was made with government support under grant noW81XWH-16-1-0701 awarded by the Department of Defense/DARPA. Thegovernment has certain rights in this invention.

BACKGROUND

Exoskeletons, such as powered exoskeletons, are used for variouspurposes, such as rehabilitation, assistance, strength amplification,productivity enhancement, and/or others. Powered exoskeletons operate bytransmitting a controlled amount of torque to the wearer's body.However, transmitting torque to the wearer's body in a safe,comfortable, and/or effective manner is associated with many challenges.For example, high variability exists anatomical measurements andproportions between different humans. Furthermore, the shape and/orvolume of human limbs varies with muscle activation and physicalinteraction with exoskeletons. A particular challenge in the effectiveimplementation of exoskeletons is associated with aligning rotationaland/or translational axes of exoskeletons (e.g., artificial joints) withanatomical rotational and/or translational axes of human users (e.g.,anatomical joints).

Misalignments between artificial joints and anatomical joints may resultin spurious forces and/or torques applied to the user. Spurious forcesand/or torques may in turn produce unwanted load on the anatomicaljoints and/or shear stress on the user's skin. Such unwanted load and/orshear stress can reduce user comfort and/or user safety when operatingan exoskeleton.

Accordingly, there is an ongoing need for mechanisms capable ofimproving exoskeletons. In particular, there is an ongoing need formechanisms that can effectively align anatomical joints with artificialjoints of exoskeletons.

The subject matter claimed herein is not limited to embodiments thatsolve any disadvantages or that operate only in environments such asthose described above. Rather, this background is only provided toillustrate one exemplary technology area where some embodimentsdescribed herein may be practiced.

SUMMARY

Disclosed herein are self-aligning mechanisms that may be utilized inexoskeletons (powered or non-powered) to dynamically align anatomicaland exoskeleton joints. An exoskeleton including the self-aligningmechanisms can be configured to adjust to individual user's uniquekinesiology and motion to avoid or reduce uncomfortable or injuriousspurious forces and/or torques to the user.

The self-aligning mechanisms use a combination of prismatic and revolutepassive degrees of freedom and/or elastic elements to dynamically alignthe anatomical and artificial joint. The self-aligning mechanism isadded in series into the human-robot kinematic chain These self-aligningmechanisms may be utilized in passive or powered exoskeletons (ororthoses), such as a powered hip exoskeleton or a powered kneeexoskeleton.

The self-aligning mechanisms beneficially function to provide dynamicalignment of the actuated and anatomical axis in a manner that accountsfor variations in user anthropometry, while also beneficially minimizingstress on the user's joint and soft tissues. The self-aligningmechanisms are configured to transmit torque to the intended joint whilereducing undesired loads on the limb.

The self-aligning mechanisms described herein allow for dynamicalignment of the actuated and anatomical axis for various types of useranatomies. This allows for exoskeletons with reduced need ofcustomization and potentially less weight due to the decreased need forindividual customization features.

Some embodiments provide an exoskeleton device that includes anartificial joint and a frame member extending from the artificial joint.The frame member is configured for extension over a limb of a user. Theexoskeleton device also includes a self-aligning mechanism connected tothe frame member. The self-aligning mechanism includes three passivedegrees of freedom (pDOF) provided in a prismatic-revolute-revolute(PRR) configuration. The self-aligning mechanism also includes a limbattachment member configured for mechanically coupling to a portion ofthe limb of the user.

Some embodiments provide a method for facilitating exoskeleton-assistedmovement. The method includes arranging an exoskeleton device on a userlimb with an artificial joint of the exoskeleton device positioned abouta joint of the user limb. The method also includes applying a force to afirst portion and a second portion of the user limb with the exoskeletondevice. The first portion and the second portion of the user limb are onopposing longitudinal sides of the joint of the user limb. Furthermore,the method includes compensating for misalignment between the artificialjoint and the joint of the user limb with a self-aligning mechanism ofthe exoskeleton device. The self-aligning mechanism is positioned aboutthe first portion of the user limb, and the self-aligning mechanismincludes three passive degrees of freedom (pDOF) provided in aprismatic-revolute-revolute (PRR) configuration. The compensationcontributes to reduced spurious forces and/or torques exerted on thefirst portion of the user limb by the exoskeleton device.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an indication of the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features can be obtained, a more particular descriptionof the subject matter briefly described above will be rendered byreference to specific embodiments which are illustrated in the appendeddrawings. Understanding that these drawings depict only typicalembodiments and are not therefore to be considered limiting in scope,embodiments will be described and explained with additional specificityand detail through the use of the accompanying drawings.

FIG. 1 illustrates a perspective view of example components of anexoskeleton device in a partially extended configuration;

FIG. 2 illustrates a perspective view of an example exoskeleton devicesecured to a limb of a user in a flexed configuration;

FIG. 3 illustrates a side view of an example self-aligning mechanism ofan exoskeleton device;

FIGS. 4A-4C illustrate schematic diagrams of different ways of attachingexoskeleton devices to user limbs;

FIG. 5 illustrates a block diagram of control and signal processingsystems associated with an exoskeleton device;

FIGS. 6A-9 illustrate graphs of forces and torques applied to a portionof a user's limb by exoskeleton devices when using a self-aligningmechanism and when not using a self-aligning mechanism;

FIG. 10 illustrates a perspective view of example components of a hipexoskeleton, in accordance with the present disclosure;

FIG. 11 illustrates a close-up perspective view of a lower interface ofa hip exoskeleton; and

FIG. 12 illustrates a close-up perspective view of an upper interface ofa hip exoskeleton.

DETAILED DESCRIPTION Overview

Disclosed embodiments are directed to self-aligning mechanisms inpassive and powered exoskeletons. Those skilled in the art willappreciate, in view of the present disclosure, that at least some of theembodiments disclosed herein may address various shortcomings associatedwith conventional exoskeletons.

For example, the self-aligning mechanisms of the present disclosure usea combination of prismatic and revolute passive degrees of freedom(pDOF) and/or elastic elements to dynamically align the anatomical andartificial joint. The self-aligning mechanisms are configured totransmit torque to the intended joint while reducing undesired loads onthe limb. In some instances, the range of motion of the pDOFs of theself-aligning mechanisms of the present disclosure is substantiallyunaffected by differences in assistive torque applied or by misalignmentbetween the artificial joint and the anatomical joint (e.g., indicatingnegligible friction in the pDOFs).

An exoskeleton device, as described herein, may be used to facilitateexoskeleton-assisted movement of a user limb. For example, a method forfacilitating exoskeleton-assisted movement, in accordance with thepresent disclosure, may include various acts, such as arranging anexoskeleton device on a user limb, with an artificial joint of theexoskeleton device positioned about a joint of the user limb. A forcemay be applied by the exoskeleton device to first and second portions ofthe user limb (where the first and second portions of the user limb areon opposing longitudinal sides of the joint of the user limb). Aself-aligning mechanism of the exoskeleton device, positioned about thefirst portion of the user limb, may advantageously compensate formisalignment between the artificial joint and the joint of the userlimb. Such compensation contributes to reduced spurious forces and/ortorques exerted on the first portion of the user limb by the exoskeletondevice.

For instance, in one example implementation of a knee exoskeleton thatincludes a self-aligning mechanism in accordance with the presentdisclosure, peak spurious forces applied to the user's shank are below10 N (e.g., about 5 N) and peak spurious torques applied to the user'sshank are below 1 Nm (e.g., about 0.5 Nm) for an assistive torque ofabout 50 Nm applied by the knee exoskeleton (in a sit-to-standexperiment). By way of contrast, for a knee exoskeleton without aself-aligning mechanism, peak spurious forces and torques are typicallywithin a range of about 50 N and 10 Nm, respectively.

The self-aligning mechanisms described herein allow for dynamicalignment of the actuated and anatomical axis for various types of useranatomies. This allows for exoskeletons with reduced need ofcustomization and potentially less weight due to the decreased need forindividual customization features. Furthermore, at least someexoskeletons of the present disclosure comprise a substantiallysymmetric artificial joint and/or frame structure, advantageouslyallowing the exoskeletons to be used on both right limbs and left limbs(e.g., on a user's right leg or a user's left leg) in the alternativewithout hardware modifications.

In addition, the self-aligning mechanisms of the present disclosure maybe constructed in an advantageously lightweight manner so as to formonly a small proportion of the total weight of the exoskeleton. Forexample, in some implementations, the self-aligning mechanism onlyaccounts for less than about 6% (e.g., 5.3%, or 190 g) of the totalweight of the exoskeleton (e.g., about 3.6 kg).

Having described some of the various high-level features and benefits ofthe disclosed embodiments, attention will now be directed to FIGS. 1through 12 . These Figures illustrate various supporting illustrationsrelated to the disclosed embodiments.

Example Exoskeleton Devices

FIG. 1 illustrates a perspective view of example components of anexoskeleton device 100. The exoskeleton device 100 depicted in FIG. 1 isadapted for selectively applying power and/or torque to a user's kneejoint (e.g., for assisting individuals with lower limb impairments).Although the exoskeleton device 100 of FIG. 1 may be regarded as a kneeexoskeleton, the principles and techniques described herein may beapplied to exoskeletons adapted for providing assistance to other bodilystructures (e.g., waist, elbow, wrist, ankle, and/or otherexoskeletons).

In the embodiment shown in FIG. 1 , the exoskeleton device 100 includesan artificial joint 102 formed from a first component 102A and a secondcomponent 102B. The first component 102A is arranged on the exoskeletondevice 100 for positioning on a first lateral side of a human joint(e.g., a human knee), whereas the second component 102B is arranged onthe exoskeleton device 100 for positioning on a second, opposing lateralside of the human joint (see FIG. 2 ).

As is illustrated in FIG. 1 , the artificial joint 102 of theexoskeleton device 100 comprises a rotation point between a thighsection 104 of the exoskeleton device 100 and a shank section 106 of theexoskeleton device 100. The artificial joint 102 may be formed, in someinstances, using steel shafts and low friction plastic bushings, and/orother rotational mechanisms. The exoskeleton device 100 may apply anassistive torque to rotate the shank section 106 relative to the thighsection 104 about the artificial joint 102. In this way, when theexoskeleton device 100 is worn on a leg of a user, the assistive torqueapplies forces to the thigh and shank of the user's leg to provideassisted rotation of the user's knee about the user's knee joint.

To facilitate such functionality, the example exoskeleton device 100depicted in FIG. 1 includes a slider-crank mechanism 108, which isconnected to the artificial joint 102 and powered by a linear actuator110. The slider-crank mechanism 108 of FIG. 1 includes separateslider-crank structures forming a four-bar mechanism. For example, asshown in FIG. 1 , the separate slider-crank structures include arespective crank 112A, 112B connected to a frame member 114 that is alsoconnected to the artificial joint components 102A and 102B. Therespective cranks 112A and 112B connect via respective couplers 116A,116B to respective sliders 118A, 118B, and the respective sliders 118A,118B are connected at respective slider joints 120A and 120B. Therespective slider joints 120A and 120B are configured to be driven bythe linear actuator 110 and to travel along a rail 126 that extendsalong the thigh section 104 (e.g., along the top of a user's thigh).

The linear actuator 110 may take on any suitable form for actuating theslider joints 120A and 120B, such as a reaction force sensing elasticactuator (RFSEA). In some implementations, the actuator uses a ballscrew system (e.g., 8×2 mm) where the nut is driven by a timing belt andsupported by two angular contact bearings. The belt pulley system may,in some instances, have a 2.5:1 transmission ratio and be connected to abrushless DC motor. The actuator may feature a sliding element that actsas a bridge between the actuation system and the ground. This slidingelement may anchor directly to the exoskeleton thigh frame and beconnected to the actuation part through two pre-compressed coil springs.The ball screw may be supported by a low-friction linear guide thatprevents radial loading on the ball screw.

The locations of the respective sliders 118A, 118B may impose aconstraint on the offset of the four-bar mechanism (e.g., the distancebetween the artificial joints components 102A, 102B and the connectionpoints of the cranks 112A, 112B to the frame member 114. The offset ofthe four-bar mechanism may be modified to tailor to the thigh dimensionsof the expected user and/or class of users (e.g., 103 mm for a 50^(th)percentile male thigh).

FIG. 1 illustrates the exoskeleton device 100 in a partially extendedconfiguration. The shank section 106 of the exoskeleton device 100 maybe rotated relative to the thigh section 104 of the exoskeleton deviceabout the artificial joint 102 to a full flexion position or a fullextension position or to any position therebetween (e.g., by actuationof the linear actuator 110).

Furthermore, in some implementations, the exoskeleton device 100includes a flexion end stop 122 integrated into the integrated into thethigh section 104 to limit the range of motion of the linear actuator110 (e.g., resulting in a 100-degree maximum flexion knee angle, orother maximum flexion angle). Still furthermore, in someimplementations, the exoskeleton device 100 includes extension end stops124A, 124B integrated on frames of the thigh section 104 and the shanksection 106 to prevent the artificial joint 102 (and any attachedanatomical joint) from hyperextending

FIG. 1 also illustrates that the exoskeleton device 100 can includeelectronics 128 (the functions and structure of which will be describedhereinafter).

FIG. 2 illustrates a perspective view of the exoskeleton device 100secured to a limb of a user (in a partially flexed configuration). Thelimb of the user represented in FIG. 2 comprises the right leg 202 ofthe user. As is evident from FIG. 2 , the linear actuator 110 isconfigured to be secured over the thigh 204 of the right leg 202 of theuser.

For instance, FIG. 2 shows the linear actuator 110 affixed to a shell206 of the exoskeleton device 100. The shell 206 may comprise a flexibleplastic molded thigh shell, which may be flexible enough to allow userswith different thigh sizes and/or shapes to use the exoskeleton device100 in a comfortable manner. In some implementations, the inner surfaceof the shell 206 is lined with a hook and loop fastener (e.g., Velcro)or other fastening device, which allows the shell 206 to connect to ahip strap 208. The hip strap 208 of FIG. 2 can wrap around the user'swaist and thigh (e.g., under the shell 206) and affix to the shell 206to improve the physical connection between the exoskeleton device 100and the user.

In some implementations, the shell 206 comprises one or more additionalor alternative straps 210 to facilitate quick donning of the exoskeletondevice 100. For example, the shell 206 may include straps 210 with aspin buckle system and/or magnetic buckles to facilitate quickaffixation of the shell 206 to the thigh 204 of a user.

FIG. 2 also shows that the exoskeleton device 100 may be constructedfrom various frame members. For example, FIG. 2 illustrates a thighframe 212 extending from a terminal portion of the rail 126 that guidesthe slider joints 120A and 120B. The thigh frame 212 extends toward theartificial joint component 102A. Although FIG. 2 only illustrates asingle portion of the thigh frame 212 extending over the right portionof the user's right leg 202 toward the user's knee, the thigh frame 212may include an opposite portion extending over the left portion of theuser's right leg 202 (see FIG. 1 ).

FIG. 2 furthermore depicts the frame member 114 of the exoskeletondevice 100. In particular, FIG. 2 shows the frame member 114 extendingfrom the artificial joint 102 (or from the artificial joint components102A and 102B) over the shank 214 of the right leg 202 of the user. Inthis regard, the artificial joint 102 may be regarded, in someinstances, as an interface between the frame member 114 and the thighframe 212.

In the example implementation depicted in FIG. 2 , the frame member 114includes a bridging element 216 that is connected to both of theartificial joint components 102A and 102B at different ends of thebridging element 216 (in addition to being connected to the respectivecranks 112A and 112B). The bridging element 216 extends from thedifferent artificial joint components 102A and 102B about the leg 202 ofthe user toward a central portion 218 of the bridging element 216 (e.g.,in a C-shape). FIG. 2 furthermore illustrates a lower link 220 extendingfrom the central portion 218 of the bridging element 216 so as to extendover and along the shank 214 of the right leg 202 of the user.

FIG. 2 illustrates a self-aligning mechanism 222 attached to the lowerlink 220. The self-aligning mechanism 222 includes a limb attachmentmember 224 that is configured for mechanically coupling to the shank 214of the right leg 202 of the user, which is on the opposite longitudinalside of the knee joint of the right leg 202 relative to the thigh of theright leg 202 where the linear actuator affixes to the right leg 202.

Additional details of the self-aligning mechanism 222 will now beprovided with reference to FIG. 3 , which illustrates a side view of anexample self-aligning mechanism 222 of the exoskeleton device 100. Asnoted above, the self-aligning mechanism 222 is connected to the lowerlink 220 extending from the bridging element 216 of the frame member114.

FIG. 3 illustrates that, in some implementations, the self-aligningmechanism 222 includes three passive degrees of freedom (pDOF), whichmay be provided in a prismatic-revolute-revolute (PRR) configuration.The three pDOFs of the self-aligning mechanism 222 are, in someinstances, integrated in series with the one active revolute DOF of kneeflexion/extension facilitated by the artificial joint 102 as describedabove.

In one example, the prismatic pDOF of the self-aligning mechanism 222 isformed from a linear guide 302 connected to the lower link 220. Thelinear guide 302 may comprise a low-friction linear guide of variousspecifications (e.g., weight of about 150 g, about 750 mm range ofmotion (ROM), etc.) The directionality associated with the prismaticpDOF is illustrated in FIG. 3 by arrows 304A and 304B, indicating thatthe linear guide 302, as represented in FIG. 3 , is able to slide alongthe lower link 220.

In the example illustrated in FIG. 3 , the first revolute pDOF of theself-aligning mechanism 222 is formed by a rotary joint 306 that isconnected to the linear guide (which is slidably connected to the lowerlink 220). The rotary joint 306 may be formed in any suitable manner,and may comprise, in some instances, a multi-turn joint with nomechanical stop (however, a mechanical stop may be implemented in someembodiments). The rotational direction associated with the firstrevolute pDOF is represented in FIG. 3 by arrow 308 and rotational axis310, which indicates a rotation about a parasagittal plane of a userwhen the exoskeleton device 100 is worn on a leg of a user.

Furthermore, FIG. 3 shows that, in some instances, the second revolutepDOF of the self-aligning mechanism 222 is formed from a rotary element312 (comprising a first component 312A and a second component 312B) thatis connected to the rotary joint 306. For example, FIG. 3 illustrates ashank cuff 314 that connects to the rotary joint 306 at a centralportion of the shank cuff 314. The shank cuff 314 also connects to thecomponents 312A and 312B of the rotary element 312 on opposing ends ofthe shank cuff 314, with both components 312A and 312B of the rotaryelement 312 sharing a common rotational axis 316 (with rotationindicated by arrows 318). In this way, the rotary element 312, as shownin FIG. 3 , is configured to revolve about a rotational axis 316 that isperpendicular to the rotational axis 310 associated with the rotaryjoint 306. For instance, while the rotational axis 310 of the rotaryjoint 306 lies on a parasagittal plane, the rotational axis 316 of therotary element 312 lies on a frontal plane.

FIG. 3 illustrates the limb attachment member 224 of the self-aligningmechanism 222 affixed to the rotary element 312. In this way, the rotaryelement 312 may be regarded as connecting the limb attachment member 224to the rotary joint 306. The limb attachment member 224 may beimplemented as an adjustable strap, which allows adaptation to thedifferent limb anatomies of different users.

In some implementations, the self-aligning mechanism 222 weighs lessthan 200 g (e.g., 190 g) or weighs less than 6% of the total weight ofthe exoskeleton device 100 (e.g., 5.3%). At least some aspects of theexoskeleton device 100 described herein contribute to significantbenefits over existing exoskeleton systems.

For example, FIGS. 4A-4C illustrate schematic diagrams of different waysof attaching exoskeleton systems to user limbs (e.g., user legs). Asdepicted in FIGS. 4A-4C, F_(exo) is the force applied by the exoskeletonand F_(h) is the reaction force of the human limb. FIG. 4A illustrates aconventional exoskeleton system mounted to a user limb with assistivetorque elements arranged lateral to the user limb, which causes atorsional moment M to be created by the F_(exo) and F_(h) couple.

In contrast with the approach shown in FIG. 4A, at least someimplementations of the present disclosure use (i) the attachmentconfiguration shown in FIG. 4B at the shank, where the force istransmitted to the limb through a soft flexible strap attached to theframe on both sides, and (ii) the attachment configuration shown in FIG.4C at the thigh, where the force is transmitted through a soft flexiblestrap attached to a frame on the front of the limb. The configurationillustrated in FIG. 4B is facilitated at least in part by the placementof the first component 102A and the second component 102B of theartificial joint in parasagittal offset from the joint of the limb ofthe user, while the configuration illustrated om FIG. 4C issimultaneously facilitated at least in part by placement of the linearactuator 110 in parasagittal alignment with the joint of the limb of theuser.

In this symmetric design configuration depicted in FIGS. 4B and 4C, theassistive exoskeleton force (F_(exo)) intersects the limb central axis.Thus, it generates no torsional moment (M), and thereby provides a keyadvantage over conventional exoskeleton systems. Thus, shear stress onthe user's skin, which may cause discomfort and even pain, may beavoided. In addition, torsion on the exoskeleton frame at the point ofcontact with the user may be avoided by the design configurationdepicted in FIGS. 4B and 4C. Thus, this configuration(s) disclosedherein can help the self-aligning mechanism 222 to avoid torsion (e.g.,which could result in binding of the mechanism and, generally, mayrequire heavier and bulkier structures and/or increased designcomplexity).

In some implementations, the symmetric design of the exoskeleton device100 is facilitated by structuring each segment of the exoskeleton framefrom two symmetrical halves for wrapping around the user's limb. Thesymmetric design can configure the exoskeleton device 100 for securementto a right leg of the user or to a left leg of the user withoutsignificant hardware modifications (e.g., the exoskeleton device 100 canbe reversibly worn on a user's right leg or a user's left leg). Theexoskeleton frame may be machined from any suitable material(s), such as7075 aluminum alloy. These halves may be designed to fit any size rangeof users (e.g., a 50^(th) percentile male adult, resulting in 160 mm and115 mm in diameter of the thigh and shank sections 104 and 106,respectfully), and/or may be selectively resizable (e.g., via the use ofspacers).

Sensors and Embedded Electronics

FIG. 5 illustrates an example block diagram of control and signalprocessing systems and/or techniques associated with an exoskeletondevice 100. The exoskeleton devices of the present disclosure maycomprise an array of sensors to accurately control the human-robotinteraction (e.g., electronics 128). For instance, an exoskeleton devicemay include an absolute magnetic rotary encoder placed on theartificial/actuated joint of the exoskeleton for estimating the absoluteknee joint position. An incremental magnetic rotary encoder located onthe motor shaft may measure the position of the knee joint and may beused to estimate motor angular velocity. In addition, the linearactuator (e.g., RFSEA) may be equipped with a high-resolution rotaryabsolute encoder that measures the deflection of the linear springsusing a capstan coupling. The capstan coupling converts the lineardisplacement due to the deflection of the springs into a proportionalangular displacement of the encoder shaft, which may be driven by acable (e.g., a steel cable).

For the purpose of testing, a 6-axis load cell may be integrated intothe exoskeleton shank section to accurately measure the physicalinteraction between the user and the robot as necessary to assess thefunction of the self-aligning mechanism. The 6-axis load cell may use anoff-the-shelf signal amplifier and a custom acquisition board. The forceand torque recordings from the 6-axis load cell may be synchronized withthe exoskeleton controller using a digital signal.

The exoskeleton device may be controlled, in some instances, using acustom embedded system including two different processing units that runthe control routines and the secondary functions such as data loggingand Wi-Fi communications. All time-critical routines such as sensorreading, filtering, joint position and torque control loops, may run at2 kHz on a 32-bit microprocessor. The microprocessor may communicatewith the motor current servo controller using PWM. The high-levelcontrol loops, data-logging, and user-communication may run on asingle-board computer (e.g., at 500 Hz).

The single-board computer may communicate with the microprocessor usingSPI. An external device may run a custom GUI for data monitoring andparameter-selection purposes and may communicate via using Wi-Fi withthe single-board computer. The GUI may be used to change the controlparameters and start/stop data saving. In addition, the control systemmay use a 1050 mAh 6-cell lithium-polymer battery, and/or a 5-Vregulator to power the processing units, embedded sensors, and currentservo controller. In some implementations, the electrical powerconsumption is 3.8 W and 3.1 W with Wi-Fi on and off, respectively.Furthermore, in some implementations, the weight of the embeddedelectrical system, including battery and protective covers, is 1.1 kg.

FIG. 5 illustrates an example control system that may be utilized inconjunction with the illustrated exoskeleton device or with other suchexoskeleton devices integrating self-aligning mechanisms. At thehigh-level, a controller based on a finite-state machine defines thedesired knee torque. At the low-level, a closed-loop torque controllerwith disturbance observer defines the desired motor current that is thenimposed using a current driver. Raw signals are processed in theembedded electronics to estimate the angular position and torque at theknee joint.

A block diagram of the sensor processing is shown in FIG. 5 . Atstartup, the absolute encoder (θ_(joint)) estimates the absoluteposition of the slider (x₀) using the inverted four-bar kinematics(TR_((θ) _(joint)) ⁻¹. The absolute position of the slider is then usedin combination with a relative slider position (x_(spindle)) estimatedfrom the motor encoder (θ_(motor)), to obtain an accurate (e.g.,+/−0.011 mm) measurement of the slider position ({circumflex over (x)}).The slider position is used to calculate the position-dependenttransmission ratio of the four-bar kinematics (TR({circumflex over(x)})). Similarly, the knee joint torque (T_(joint) ^(meas)) isestimated using the spring force (F_(spring)) combined with transmissionratio (TR({circumflex over (x)})). The spring force (F_(spring)) isestimated by measuring the spring deflection (θ_(spring)) in combinationwith the stiffness of the springs (K_(s)) and the transmission ratio(TR({circumflex over (x)})).

At the low-level, a closed-loop controller is used to accurately trackthe desired knee-space torque (T_(joint) ^(des)). First, the desiredknee-space torque (T_(joint) ^(des)) is transformed into an equivalentdesired motor-space torque (T_(motor) ^(des)) using the four-bartransmission ratio (TR({circumflex over (x)})) and the combinedtiming-belt/ball screw transmission ratio (RR). The desired motor torqueis then fed to a closed-loop proportional-integral-derivative (PID)regulator with disturbance observer (DOB). The RFSEA is modeled as asecond-order system (P_(c)) as follows:

${P_{c}(s)} = {\frac{800,000}{{84.98s^{2}} + {4674s} + {800,000}}.}$

Exogenous forces and torques are handled as disturbances and fed asinputs to the system to compensate for the observed torques notresulting from the modeled system using feedforward (Q_(FF)) andfeedback filters (Q). Finally, the desired motor torque (T_(motor)^(des)) is transmitted to the off-the-shelf current driver on the kneeexoskeleton.

At the high-level, a torque-angle relationship based on healthybiomechanics defines the desired knee torque (T_(joint) ^(des)) duringsit-to-stand transitions solely as a function of the knee joint position(θ_(joint)). As can be seen in FIG. 5 , the desired knee torque startsat zero when the subject is seated, and the knee joint is flexed. As theuser stands-up, the exoskeleton knee joint starts extending from itsresting position. As a result, the desired exoskeleton torque increasesfrom zero to a maximum value (T_(max)). From its maximum, the torquedecreases with the knee joint position, finally reaching zero when theknee joint is fully extended. Notably, the user's knee angle at thestart of the sit-to-stand transition depends on the user'santhropometry, chair height, and posture. To accommodate thisvariability, the knee angle at which the exoskeleton starts providingtorque (θ_(start)) equals the measured knee angle when the sit-to-standcontroller is activated. Moreover, the desired peak torque (T_(max)) canbe adjusted by the experimenter through a GUI. The knee angle at whichthe peak torque (θ_(max)) is achieved, in some instances, at 30% betweenthe starting and the ending angle. The torque-angle relationship may beimplemented with a parametric Look-Up Table (LUT).

Example Results

FIGS. 6A-9 illustrate graphs of forces and torques applied to a portionof a user's limb by exoskeleton devices when using a self-aligningmechanism and when not using a self-aligning mechanism. In particular,the graphs represented by FIGS. 6A-9 were obtained according to anexperimental protocol using an exoskeleton device 100 as describedherein. The experimental protocol included two tasks: (i) standing upwhile assisted by the exoskeleton and (ii) tracking a desired positionagainst a virtual impedance field generated by the powered exoskeleton.Both tasks were performed by subjects with the self-aligning mechanismin a “locked” configuration (with translation/rotation of the pDOFs ofthe self-aligning mechanism restricted) and with the self-aligningmechanism in an “unlocked” configuration (with translation/rotation ofthe pDOFs unrestricted).

The results show that the self-aligning mechanism (e.g., self-aligningmechanism 222, as discussed above) significantly reduces the spuriousforces and torques on the user for both tasks. The results of theexperimental protocol also demonstrated an increased level of usercomfort facilitated by the reduction in spurious forces and torques.These results demonstrate the efficacy of self-aligning mechanisms inimproving comfort and performance during sit-to-stand and positiontracking tasks with a powered knee exoskeleton.

The mass of the self-aligning mechanism, which is not considered intheoretical models, has a critical, negative effect on its function. Forexample, gravity can cause the prismatic pDOF of a self-aligningmechanism to slide and reach its mechanical end-stop, effectivelyimpairing the self-aligning function. Similarly, inertial forces andtorques due to the mass of the self-aligning mechanism can cause itspassive joints to move during activity. These unmodeled and uncontrolledmovements are likely to limit the potential reduction of spurious forcesand torques and can cause discomfort to the user. Thus, utilizing arelatively small mass for a self-aligning mechanism as described herein(e.g., about 190 g, about 5.3% of the overall exoskeleton mass, etc.)contributes to the observed improvements in comfort and performance.

Reducing the mass of a self-aligning mechanism without impairing itsfunction under load is associated with many challenges, in particularbecause the passive joints of a self-aligning mechanism must be able tomove freely while transferring the assistive torque. For example, theprismatic joint/pDOF must be able to slide freely while transferring theforce F_(z) (see FIG. 6C) so that the powered exoskeleton can provideassistive or resistive torques at the user's knee joint. In someimplementations, a relatively large linear guide 302 is used (150 g, 3.5kN max load). Although a smaller and lighter linear guide would reducethe overall mass, it may increase friction, which could impair themovement of the passive joints under load.

Notably, the symmetric design of the powered exoskeleton as discussedabove has a beneficial effect on the function of the self-aligningmechanism. The symmetric design minimizes the torque on the linearguide, allowing for both the mass and the friction of the self-aligningmechanism to be minimized. Similarly, the symmetric design reduces theload that the linkages of the self-aligning mechanism must withstand.This load reduction is beneficial because deformations in the linkagesof the self-aligning mechanism may impair the ability of its passivejoints to move freely under load.

The comfort and effort during each experimental condition were assessedusing questionnaires filled out by the subjects at the end of each test(i.e., standing-up and tracking tasks, with the exoskeleton device inlocked and unlocked configurations). The results show that the presenceof the self-aligning mechanism significantly improves comfort duringboth the standing-up and the tracking task. Interestingly, the trackingtask was reported to be significantly more comfortable than thestanding-up task. This result may be explained by the fact that thespurious forces and torques were greater during the standing-up taskthan the tracking tasks. Thus, these results suggest that there is acorrelation between the spurious forces and torques and the user'scomfort. The results suggest that these interaction forces and torqueswere large enough for the subjects to feel less comfortable using thelocked configuration than when using the unlocked configuration.

Performance during the standing-up task was assessed using theroot-mean-square error between the center of pressure (CoP) and themidline of a force plate on the self-aligning mechanism and the maximumdeviation of the CoP from the midline. The results show that bothperformance metrics were significantly better (up to 32%) in thepresence of the self-aligning mechanism (i.e., under the unlockedconfiguration). Performance during the tracking task was assessed usingthe RMS error between the target wave and measured knee angle. The RMSerror was significantly lower in the unlocked configuration than thelocked configuration (38%).

FIGS. 6A-6F illustrate the mean values of the interaction forces andtorques between the subjects' shank and the exoskeleton device duringthe sit-to-stand (STS) task with the exoskeleton device under locked andunlocked configurations. FIG. 7 provides a bar plot of absolute valuesof average forces and torques for the STS task for both the locked andunlocked configurations, with error bars showing standard error.Similarly, FIGS. 8A-8F illustrate the mean values of the interactionforces and torques between the subjects' shank and the exoskeletondevice during the tracking (TRK) task with the exoskeleton device underlocked and unlocked configurations. FIG. 9 provides a bar plot ofabsolute values of average forces and torques for the TRL task for boththe locked and unlocked configurations, with error bars showing standarderror.

As is evident from FIGS. 6A-9 , the averages of F_(y) and F_(z) aresimilar for the locked and unlocked configurations during thestanding-up task but not for the tracking task. Furthermore, FIGS. 6A-9show that, during the tracking task, F_(y) and F_(z) appear to followsimilar trajectories, however, under the unlocked configuration, thedata is offset compared to the locked configuration. This variation inF_(y) and F_(z) between conditions may have been caused by the positionof the loadcell with respect to the active joint of the poweredexoskeleton, which may change when the self-aligning mechanism is in theunlocked condition because the loadcell can slide along the frame of theexoskeleton. Interestingly, during the standing-up task, the averagevalue of F_(z) is slightly higher in the unlocked configuration than inthe locked configuration. With the unlocked configuration, only F_(z)contributes to generating the desired flexion/extension torque on theuser's knee. In contrast, with the locked configuration, both F_(z) andT_(y) contribute to transfer the knee flexion/extension torque to theuser's knee, indicating a potential for a purer translation of torquebetween the exoskeleton and the human limb during the unlockedconfiguration.

The results shown in FIGS. 6A-9 show that the presence of theself-aligning mechanism (i.e., the unlocked configuration) can lead to asignificant decrease in the average values for F_(x), T_(y), and T_(z)during both standing-up and tracking tasks. This reduction isfacilitated at least in part by the self-aligning mechanism implementedin the exoskeleton device that comprises three pDOFs, allowingtranslational movements along a first axis and rotational movementsaround the two additional axes that are perpendicular to one another.These result shows that the proposed self-aligning mechanism has asignificant effect on spurious forces and torques. For differentspecific kinematics or mechanical implementations, a self-aligningmechanism can be used to achieve similar comfort and performanceimprovement, provided it can show a similar reduction in spurious forcesand torques.

Additional Embodiments

As indicated hereinabove, a self-aligning mechanism may be implementedon various types of exoskeleton devices and are not limited to kneeexoskeletons. For example, FIG. 10 illustrates a hip exoskeleton 1000,which includes a lower interface 1002 for connecting to a thigh of auser as well as an upper interface 1004 for connecting to a hip of auser. The lower interface 1002 includes a thigh cuff 1006 (e.g., formedfrom rigid plastic and nylon straps) as well as elastic elements 1008(e.g., thick surgical rubber) for securing to a thigh of a user (e.g.,forming a thigh orthosis). The thigh orthosis distributes resultantforces across a large portion of the distal thigh and may include loaddistributing bars 1016.

The upper interface 1004 includes an attachment member 1010 that isconfigured to connect to a pelvis pad (not shown) that wraps around theuser's hips (e.g., forming a pelvis orthosis). A pelvis orthosis mayinclude separate elements for attachment to opposing sides of the pelvisof a user. The separate elements may be connected by straps (e.g., spinbuckle straps). The pelvis orthosis may include an anti torsion bar thatresists independent movement of the pelvis orthosis and transferssagittal plane moments to the sacral and lumbar portions of the lowerback. The anti-torsion bar may also store the electronics and/or batteryfor the hip exoskeleton 1000.

The hip exoskeleton 1000 includes an artificial joint 1012 configuredfor positioning about the hip of the user to provide an active DOF forfacilitating the application of assistive torque to the hip of the user.

The hip exoskeleton 1000 of FIG. 10 utilizes an offset slider-crankmechanism 1014 to facilitate assistive torque. In some implementations,the offset slider-crank mechanism 1014 may be powered by a linearactuator (e.g., including a brushless DC motor and a primary helicalgear transmission) coupled with a high-efficiency ball screw. A linearguide may support the perpendicular load on the ball screw nut. Angularcontact ball bearings may support radial and axial loads on the helicalgears, and translation of the screw nut and linear guide block along therail may be converted to rotation of the actuated artificial joint 1012through composite compliant bars, creating a series elastic actuator.Lightweight, low-friction dry bushings may support the load of theactuated artificial joint 1012.

FIG. 11 illustrates a close-up view of the lower interface 1002 of thehip exoskeleton 1000. As is illustrated in FIG. 11 , the lower interface1002 includes a self-alignment mechanism 1102 to facilitate a reductionin spurious forces and torques that become applied to the user's hip. Inparticular, the self-alignment mechanism 1102 comprises one or morerails 1104 with one or more linear guides 1106 attached thereto (e.g.,with corresponding rails and linear guides on multiple sides of theshaft 1110 of the hip exoskeleton 1000), providing a prismatic pDOF(with directionality indicated by arrows 1108A and 1108B).

The self-alignment mechanism 1102 also includes a revolute pDOF providedby a rotary joint 1112 coupled to the one or more linear guides 1106 andconnected to the thigh cuff 1006 to facilitate passive rotation of thethigh cuff 1006 about an axis that is perpendicular to the translationalaxis associated with the prismatic pDOF (indicated in FIG. 11 by axis1114 and arrow 1116). The self-alignment mechanism 1102 contributes to areduction in the spurious forces and torques applied by the hipexoskeleton 1000 to the user's body.

FIG. 12 illustrates a close-up view of the upper interface 1004 of thehip exoskeleton 1000. In particular, FIG. 12 illustrates that the upperinterface 1004 may comprise a separate self-alignment mechanism 1202that includes a pair of revolute pDOFs formed by separate rotary joints1204A and 1204B and that are configured in series with the active DOF ofthe artificial joint 1012. The pDOFs of the self-aligning mechanism 1202may allow for unconstrained hip abduction and/or adduction. The pair ofrevolute pDOFs rotate about parallel rotational axes 1206A and 1206B(indicated by arrows 1208A and 1208B). The self-alignment mechanism 1202contributes to a reduction in the spurious forces and torques arisingfrom any misalignment between the powered flexion/extension axis of thehip exoskeleton 1000 and the user's anatomical flexion/extension axis,particularly in combination with the self-alignment mechanism 1102.

The following provides an overview of example sensing and powerelectronics that may be implemented with a hip exoskeleton 1000. The hipexoskeleton 1000 may include a power supply, such as a 1200 mAh,six-cell lithium-ion (LiIon) battery. A 5-V regulator may be implementedto scale the supply voltage as needed to power the embedded computer andanalog sensors. A 3.3-V regulator may power the microcontroller andoperate as the logic voltage for the digital sensors. Two separateprocessing units may be implemented in the motherboard to run thecontrol routines and secondary functions, such as data saving and Wi-Ficommunications. All time-critical routines, such as sensor reading,filtering, joint position, torque control loops, etc., may run at 1 KHzon a microcontroller (e.g., a 32-bit microcontroller). Themicrocontroller may use pulse-width modulation (PWM) to communicate tothe two motor servo drives, which run the closed-loop motor currentcontrol at 50 kHz.

The microcontroller may use dedicated serial peripheral interface (SPI)busses to communicate with the embedded sensors and an embedded,single-board computer, which may run the high-level control loops, datasaving, and user communication (e.g., at 500 Hz). The embeddedsingle-board computer may communicate with a remote device using Wi-Fi.The remote device may run a custom graphical user interface (GUI) fordata monitoring and parameter-selection purposes. Using the GUI, a usercan modify the high-level control parameters while the device isoperating. The operating system for the embedded computer may be storedon a single SD card, which may also be used for data storage. Themicroprocessor, the embedded single-board computer, the motor servodrives, and the voltage regulators may be integrated on a custommotherboard. The electrical system, including the power supply, may befully enclosed in a custom protection cover, which may connect to theback of the pelvis interface. In some implementations, the electricalpower consumption is 3.6 W and 3.1 W, respectively, with Wi-Fi on andoff

Sensor circuit boards may be housed within the hip exoskeleton frame. A14-bit magnetic absolute encoder board may measure the hipflexion/extension angle and be located at the proximal end of the carbonfiber frame. An inertial measurement unit (IMU) board may measure theaccelerations and rotational speeds and be located at the distal end ofthe carbon fiber frame. Both custom circuit boards may communicate withthe microcontroller using SPI. A dedicated, shielded wire may be used totransmit the digital data from the sensors to the motherboard. Anincremental encoder may be used to measure the position of the motorshaft for torque control purposes. Hall sensors embedded in the motormay be used for commutation by the servo drives. The signal from theincremental encoder and hall sensors may be transmitted to themotherboard using a dedicated shielded wire. Another cable carrying themotor power stage current may connect the exoskeleton to themotherboard.

A hierarchical controller may provide synchronous assistance duringambulation. At the high-level, an adaptive frequency oscillator (AdOsc)may estimate the gait cadence of the coupled human-exoskeleton system.Estimation of the cadence may be combined with information about thestart of the gait cycle to provide a continuous estimate of the gaitcycle evolution (e.g., 0-100% stride completion). The peak of the hipextension angle may be used as the start of the gait cycle.

A finite-state machine may detect the peak of the hip flexion angle,indicating the start of the gait cycle. The finite state machine mayinclude two states: peak flexion and swing preparation/initiation, andthe state machine may take as input the angular orientation and velocityof the thigh in the sagittal plane. These input variables may beestimated by a complementary filter combining the accelerometer andgyroscope data from the IMU. A low-pass filter may be applied to thethigh orientation to reduce noise and increase robustness. Notably, thedelay introduced by the filter may be accounted for when tuning thetiming of the assistance. When the thigh orientation is higher than apredefined threshold (e.g., the hip joint is flexed) and the thighvelocity is lower than a predefined negative threshold (e.g., the thighis extending), the finite-state machine may transition between peakflexion state and swing preparation/initiation state. This transitionmay indicate that a suitable peak of hip flexion has been detected,triggering the start of the gait cycle. From swingpreparation/initiation state, the finite state machine may transitionback to peak flexion state when the thigh orientation is lower than apredefined threshold (i.e., the hip joint is extended).

The powered hip exoskeleton 1000 can be used in bilateral or unilateralconfiguration, and the two actuation modules may be interchangeable.Each actuation module may have a dedicated finite-state machine andadaptive oscillator. When the exoskeleton is used bilaterally, the usermay have the option to use dedicated finite-state machines and adaptiveoscillators for each actuation module. In this case, the modules arecontrolled independently of one another, using their own percent strideestimate to generate assistance. Alternatively, the user may have theoption to select the finite-state machine and adaptive oscillator of oneactuation module to control both actuation modules. If the user choosesto use the finite-state machine and adaptive oscillator from only oneactuation module, then the desired torque of the contralateral side maybe delayed by 50% of stride. The latter option can be used, for example,with hemiparetic subjects to use the unaffected side to control themovement of the affected side.

The middle-level controller defines the desired assistive torque basedon the gait phase estimate (e.g., percent stride) received from thehigh-level controller. The desired assistive torque is defined using twoGaussian functions—one for flexion and one for extension. Each Gaussianfunction may include three parameters that can be adjusted by the userthrough the graphical user interface:

${T(t)} = {{T_{flx}e^{- \frac{{({x - t_{flx}})}^{2}}{2w_{flx}^{2}}}} - {T_{ext}e^{- \frac{{({x - t_{ext}})}^{2}}{2w_{ext}^{2}}}}}$

The first parameter is the peak of the torque (i.e., T_(flx), T_(ext)).The second parameter is the timing, or percent stride, at which the peakof the torque happens (i.e., t_(flx), t_(ext)) of the peak of torque.The third parameter is the duration of the assistance, which is adjustedby changing the width of the Gaussian functions (i.e., w_(flx),w_(ext)). The desired torque obtained by the gaussian function may thenbe scaled by the user's body mass. The user has the option to usedifferent parameters for the left and right sides of the powered hipexoskeleton or to use the same parameters.

The low-level controller converts the desired assistive torque into adesired motor torque for the servo motor. The torque controller mayinclude a feedforward command based on the position-dependenttransmission ratio. This feedforward command may include a constantfactor (η) that compensates for the efficiency of the actuation system.In addition, two compensators may be implemented to modify the dynamiceffects of the transmission system on the output torque increasingfidelity and reducing the apparent impedance at the output joint. Bothcompensators may take as input the motor position measured by theincremental encoder. The first compensator may generate an onlineestimate of the viscous torque due to the linear actuator velocity. Thesecond compensator may compute a scaled and low-pass-filtered estimateof the transmission inertia. The desired current may be calculated byfirst adding the feedforward term to the compensators estimates and thendividing by the torque constant of the motor.

Although walking, running, and stairs climbing are periodic activities,the kinematic profiles are different. The periodicity of each activitymay allow the AdOsc to learn the frequency of each task, and the statemachine parameters may be further tuned to fit the kinematics.Furthermore, the peak assistance and timing are different for walking,running, and stairs. However, the high-level control algorithm is, insome instances, fundamentally unchanged between user activity.Therefore, a series of parameters may be tuned for each of the taskssuch that a desired assistance profile could be reliably generated.

Additional Exemplary Aspects

Embodiments of the present disclosure may include, but are notnecessarily limited to, features recited in the following clauses:

Clause 1: An exoskeleton device, comprising: an artificial joint; aframe member extending from the artificial joint configured forextension over a limb of a user; and a self-aligning mechanism connectedto the frame member, the self-aligning mechanism comprising threepassive degrees of freedom (pDOF) provided in aprismatic-revolute-revolute (PRR) configuration, the self-aligningmechanism comprising a limb attachment member configured formechanically coupling to a portion of the limb of the user.

Clause 2: The exoskeleton device of Clause 1, wherein the artificialjoint comprises a first component and a second component, the firstcomponent and the second component being configured for positioning onopposing lateral sides of a joint of the limb of the user.

Clause 3: The exoskeleton device of Clause 2, wherein the frame membercomprises a bridging element, the bridging element being connected toboth the first component and the second component on opposing ends ofthe bridging element, and wherein the frame member includes a lower linkextending from a central portion of the bridging element, the lower linkbeing configured to extend along the limb of the user.

Clause 4: The exoskeleton device of Clause 3, wherein a prismatic pDOFof the self-aligning mechanism is formed from a linear guide connectedto the lower link.

Clause 5: The exoskeleton device of Clause 4, wherein a first revolutepDOF of the self-aligning mechanism is formed by a rotary jointconnected to the linear guide slidably connected to the lower link.

Clause 6: The exoskeleton device of Clause 5, wherein a second revolutepDOF of the self-aligning mechanism is formed by a rotary elementconnected to the rotary joint, the rotary element being configured torevolve about a second rotational axis that is perpendicular to a firstrotational axis associated with the rotary joint.

Clause 7: The exoskeleton device of Clause 6, wherein the limbattachment member is connected to the rotary element.

Clause 8: The exoskeleton device of any one of Clauses 1-7, wherein theself-aligning mechanism weighs less than 200 g.

Clause 9: The exoskeleton device of any one of Clauses 1-8, wherein theself-aligning mechanism forms less than 6% of a total weight of theexoskeleton device.

Clause 10: The exoskeleton device of any one of Clauses 1-9, wherein theartificial joint is connected to a slider-crank mechanism, theslider-crank mechanism being powered by a linear actuator.

Clause 11: The exoskeleton device of Clause 10, wherein the artificialjoint comprises a first component and a second component configured forpositioning on opposing lateral sides of a joint of the limb of theuser, and wherein the slider-crank mechanism comprises a four-barmechanism, the four-bar mechanism comprising: a first slider-crankstructure connected between the linear actuator and the first componentof the artificial joint; and a second slider-crank structure connectedbetween the linear actuator and the second component of the artificialjoint.

Clause 12: The exoskeleton device of Clause 11, wherein the linearactuator is configured for securement over a second portion of the limbof the user, the second portion being on an opposing longitudinal sideof the joint of the limb relative to the portion of the limb of theuser.

Clause 13: The exoskeleton device of Clause 12, further comprising ashell connected to the linear actuator, the shell being configured toform about the second portion of the limb of the user.

Clause 14: The exoskeleton device of Clause 13, further comprising astrap connected to the shell and configured to secure the shell to thesecond portion of the limb of the user.

Clause 15: The exoskeleton device of any one of Clauses 12-14, whereinthe linear actuator is configured for securement over the second portionof the limb in parasagittal alignment with the joint of the limb of theuser.

Clause 16: The exoskeleton device of Clause 15, wherein the firstcomponent and the second component of the artificial joint areconfigured for positioning in parasagittal offset from the joint of thelimb of the user.

Clause 17: The exoskeleton device of any one of Clauses 12-16, whereinthe limb is a leg of the user, and wherein the portion of the limb is ashank of the leg, and wherein the second portion of the limb is a thighof the leg, and wherein the joint of the user is a knee of the leg.

Clause 18: The exoskeleton device of Clause 17, wherein the exoskeletondevice is configured for securement to a right leg of the user, andwherein the exoskeleton device is configured for securement to a leftleg of the user.

Clause 19: A method for facilitating exoskeleton-assisted movement,comprising: arranging an exoskeleton device on a user limb with anartificial joint of the exoskeleton device positioned about a joint ofthe user limb; applying a force to a first portion and a second portionof the user limb with the exoskeleton device, the first portion and thesecond portion of the user limb being on opposing longitudinal sides ofthe joint of the user limb; and compensating for misalignment betweenthe artificial joint and the joint of the user limb with a self-aligningmechanism of the exoskeleton device, the self-aligning mechanism beingpositioned about the first portion of the user limb, the self-aligningmechanism comprising three passive degrees of freedom (pDOF) provided ina prismatic-revolute-revolute (PRR) configuration, wherein thecompensation contributes to reduced spurious forces and/or torquesexerted on the first portion of the user limb by the exoskeleton device.

Clause 20: The method of Clause Error! Reference source not found.,wherein, for an assistive torque of about 50 Nm applied on the user limbby the exoskeleton device, a peak spurious force exerted on the firstportion of the user limb by the exoskeleton device is below 10 N and apeak spurious torque exerted on the first portion of the user limb bythe exoskeleton device is below 1 Nm.

Conclusion

While certain embodiments of the present disclosure have been describedin detail, with reference to specific configurations, parameters,components, elements, etcetera, the descriptions are illustrative andare not to be construed as limiting the scope of the claimed invention.

Furthermore, it should be understood that for any given element ofcomponent of a described embodiment, any of the possible alternativeslisted for that element or component may generally be used individuallyor in combination with one another, unless implicitly or explicitlystated otherwise.

In addition, unless otherwise indicated, numbers expressing quantities,constituents, distances, or other measurements used in the specificationand claims are to be understood as optionally being modified by the term“about” or its synonyms. When the terms “about,” “approximately,”“substantially,” or the like are used in conjunction with a statedamount, value, or condition, it may be taken to mean an amount, value orcondition that deviates by less than 20%, less than 10%, less than 5%,or less than 1% of the stated amount, value, or condition. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldbe construed in light of the number of reported significant digits andby applying ordinary rounding techniques.

Any headings and subheadings used herein are for organizational purposesonly and are not meant to be used to limit the scope of the descriptionor the claims.

It will also be noted that, as used in this specification and theappended claims, the singular forms “a,” “an” and “the” do not excludeplural referents unless the context clearly dictates otherwise. Thus,for example, an embodiment referencing a singular referent (e.g.,“widget”) may also include two or more such referents.

It will also be appreciated that embodiments described herein mayinclude properties, features (e.g., ingredients, components, members,elements, parts, and/or portions) described in other embodimentsdescribed herein. Accordingly, the various features of a givenembodiment can be combined with and/or incorporated into otherembodiments of the present disclosure. Thus, disclosure of certainfeatures relative to a specific embodiment of the present disclosureshould not be construed as limiting application or inclusion of saidfeatures to the specific embodiment. Rather, it will be appreciated thatother embodiments can also include such features.

1. An exoskeleton device, comprising: an artificial joint; a framemember extending from the artificial joint configured for extension overa limb of a user; and a self-aligning mechanism connected to the framemember, the self-aligning mechanism comprising three passive degrees offreedom (pDOF) provided in a prismatic-revolute-revolute (PRR)configuration, the self-aligning mechanism comprising a limb attachmentmember configured for mechanically coupling to a portion of the limb ofthe user.
 2. The exoskeleton device of claim 1, wherein the artificialjoint comprises a first component and a second component, the firstcomponent and the second component being configured for positioning onopposing lateral sides of a joint of the limb of the user.
 3. Theexoskeleton device of claim 2, wherein the frame member comprises abridging element, the bridging element being connected to both the firstcomponent and the second component on opposing ends of the bridgingelement, and wherein the frame member includes a lower link extendingfrom a central portion of the bridging element, the lower link beingconfigured to extend along the limb of the user.
 4. The exoskeletondevice of claim 3, wherein a prismatic pDOF of the self-aligningmechanism is formed from a linear guide connected to the lower link. 5.The exoskeleton device of claim 4, wherein a first revolute pDOF of theself-aligning mechanism is formed by a rotary joint connected to thelinear guide slidably connected to the lower link.
 6. The exoskeletondevice of claim 5, wherein a second revolute pDOF of the self-aligningmechanism is formed by a rotary element connected to the rotary joint,the rotary element being configured to revolve about a second rotationalaxis that is perpendicular to a first rotational axis associated withthe rotary joint.
 7. The exoskeleton device of claim 6, wherein the limbattachment member is connected to the rotary element.
 8. The exoskeletondevice of claim 1, wherein the self-aligning mechanism weighs less than200 g.
 9. The exoskeleton device of claim 1, wherein the self-aligningmechanism forms less than 6% of a total weight of the exoskeletondevice.
 10. The exoskeleton device of claim 1, wherein the artificialjoint is connected to a slider-crank mechanism, the slider-crankmechanism being powered by a linear actuator.
 11. The exoskeleton deviceof claim 10, wherein the artificial joint comprises a first componentand a second component configured for positioning on opposing lateralsides of a joint of the limb of the user, and wherein the slider-crankmechanism comprises a four-bar mechanism, the four-bar mechanismcomprising: a first slider-crank structure connected between the linearactuator and the first component of the artificial joint; and to asecond slider-crank structure connected between the linear actuator andthe second component of the artificial joint.
 12. The exoskeleton deviceof claim 11, wherein the linear actuator is configured for securementover a second portion of the limb of the user, the second portion beingon an opposing longitudinal side of the joint of the limb relative tothe portion of the limb of the user.
 13. The exoskeleton device of claim12, further comprising a shell connected to the linear actuator, theshell being configured to form about the second portion of the limb ofthe user.
 14. The exoskeleton device of claim 13, further comprising astrap connected to the shell and configured to secure the shell to thesecond portion of the limb of the user.
 15. The exoskeleton device ofclaim 12, wherein the linear actuator is configured for securement overthe second portion of the limb in parasagittal alignment with the jointof the limb of the user.
 16. The exoskeleton device of claim 15, whereinthe first component and the second component of the artificial joint areconfigured for positioning in parasagittal offset from the joint of thelimb of the user.
 17. The exoskeleton device of claim 12, wherein thelimb is a leg of the user, and wherein the portion of the limb is ashank of the leg, and wherein the second portion of the limb is a thighof the leg, and wherein the joint of the user is a knee of the leg. 18.The exoskeleton device of claim 17, wherein the exoskeleton device isconfigured for securement to a right leg of the user, and wherein theexoskeleton device is configured for securement to a left leg of theuser.
 19. A method for facilitating exoskeleton-assisted movement,comprising: arranging an exoskeleton device on a user limb with anartificial joint of the exoskeleton device positioned about a joint ofthe user limb; applying a force to a first portion and a second portionof the user limb with the exoskeleton device, the first portion and thesecond portion of the user limb being on opposing longitudinal sides ofthe joint of the user limb; and compensating for misalignment betweenthe artificial joint and the joint of the user limb with a self-aligningmechanism of the exoskeleton device, the self-aligning mechanism beingpositioned about the first portion of the user limb, the self-aligningmechanism comprising three passive degrees of freedom (pDOF) provided ina prismatic-revolute-revolute (PRR) configuration, wherein thecompensation contributes to reduced spurious forces and/or torquesexerted on the first portion of the user limb by the exoskeleton device.20. The method of claim 19, wherein, for an assistive torque of about 50Nm applied on the user limb by the exoskeleton device, a peak spuriousforce exerted on the first portion of the user limb by the exoskeletondevice is below 10 N and a peak spurious torque exerted on the firstportion of the user limb by the exoskeleton device is below 1 Nm.